DE3535889C1 - Process for the preparation of Z-2-methyl-2-butenoic acid - Google Patents

Description

the reaction times are so long that the process is no longer so economical. The temperature ranges from 70-80 ° C are therefore preferred and 70-100 ° C maintained in the two reaction stages. During the metering in of the technical nitrile in the sulfuric acid, the temperature can preferably also be kept lower, e.g. B. below 60 ° C, in particular z. B. at 30-55 ° C.

Advantageously, polymerization inhibitors are added to the reaction mixture, e.g. B. a mixture from hydroquinone and zinc sulfate. The addition of 0.1 to 1 mol% has proven to be particularly advantageous Inhibitors, based on the technical grade nitrile used.

The following example serves to further explain the invention (the percentages relate to the weight). It was a crude nitrile of the following composition (determined by gas chromatography) used:

20th

Component %

2-methyl-2-butenenitrile 63

2-methyl-3-butenenitrile 20

Cyclohexane 5.5

Vinyl cyclohexene 6.6

Cyclooctadiene 1.9

Butadiene 1.1

not defined 1.9

example

120 kg of 80 weight- % Sulfuric acid presented together with 100 g each of hydroquinone and zinc sulfate. Under cooling and Stirring was allowed to run in 81 kg (991) of crude nitrile over the course of two hours, the temperature rising to 50-55 ° C was held.

After a reaction time of 24 hours at 80 ° C., 80 liters of water were added and then for a further 32 hours at 100 ° C stirred. After adding 60 liters of toluene, the Phases separated and the organic phase fed to the distillation

After removing the low boilers, 63.5 kg of product mixture went in the boiling range of Kpie mbar 83-99 ° C, consisting of 80.5% angelica and 19.5% tiglic acid.

Residue: 18 kg.

55

eo

65

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Claims (2)

1- 2 procedures can be solved. The subject matter of the invention is a process for the production of Z-2-methyl-2-butenoic acid by sulfuric acid hydrolysis of han- 1. Process for the production of Z-2-MethyI- dels usual technical 2-methyl-2-butenenitrile at 2-butenoic acid by sulfuric acid hydrolysis at an elevated temperature and by subsequent Auskritischen 2-methyl-2-butenenitrile with increased stallisation, which is characterized in that one Temperature and subsequent crystallization of the nitrile at temperatures up to 80 ° C in 75-85, characterized in that preferably 75-8O% by weight sulfuric acid is added with stirring Nitrile is metered in at temperatures up to 80 ° C in 75 to ren until a molar ratio of nitrile to 85% by weight sulfuric acid, while stirring, a sulfuric acid of 1: 3 to 1: 1 is achieved, until a molar ratio of the nitrile to the mix then with stirring at this temperature Sulfuric acid of 1: 3 to 1: 1 is reached, the content until the nitrile groups are completely implemented then mix with stirring at this temperature, then up to a sulfuric acid content holds temperatures until the nitrile groups are completely removed from 40-60% by weight, preferably 45-55% by weight, have reacted, then diluted up to a sulfuric acid content at temperatures of up to 100 ° C diluted from 40 to 60% by weight, with stirring until the conversion to the acid has ended, the orga temperatures Stirring from up to 100 ° C until the niche phase separates from the aqueous, washes and Conversion to the acid is complete, the organic then a vacuum distillation at temperature phase separates from the aqueous, washes and subjected to up to 120 ° C, the distillate cools and then filter off the Z-2-methyl-2-butenoic acid which has crystallized out in a vacuum distillation at temperature Subjects up to 120 ° C, the distillate cools down. and the crystallized Z-2-methyl-2-butenoic acid 2-methyl-2-butenenitrile, which is used in the production filtered off. of adiponitrile as a large-scale by-product 2. The method according to claim 1, characterized and generally up to about 40 wt .-% draws that the reaction mixture Polymerisa- 25 may contain impurities, so far z. B. as tion inhibitors in a concentration of 0.1 to solvents offered on the market and even 1 mol%, based on the technical grade used in the absence of suitable other possible uses can be added. th burned. According to the data sheet of a provider, it is too 30 contains 60-70% by weight of 2-methyl-2-butenenitrile and contains generally 6-25% by weight of 2-methyl-3-butenenitrile, 0.5-9% by weight of cyclohexane, 3-7% by weight The invention relates to a new process for Her- vinylcyclohexene, to 0.1 to 4 wt .-% cyclooctadienes, position of Z-2-methyl-2-butenoic acid (2-methylisocro- to 0-2% by weight butadiene, and up to 30 ppm cyanwastonic acid, Angelicic acid, 2-methyl-cis-crotonic acid). 35 hydrogen (the components make a total of 100 This acid occurs naturally among others. as an ingredient wt .-%). Such contaminant-containing substances of angelica root oil. Some of their esters are generally referred to as "technical". the Main components of the coveted Roman camomile starting substance of the process according to the invention oil's important odor carriers. The acid and its esters will therefore also be generalized in the present application therefore useful as a smell and taste 40 in common as technical 2-methyl-2-butenenitrile or fabrics. Despite keen interest on the part of perfume-technical nitrile. meure und Flavoristen is not yet economical. The solution of the tasks is therefore particularly cal process for the preparation of the said connection surprisingly, since from a wide variety of literature fertilize known. Although EP-A-01 12 394 suggests that it is known that Z-2-methyl-2-butenoic acid and Synthesis of angelica acid and its esters by means of its derivatives willingly, for example, in the basic and in the sauthermal Rearrangement of the isomeric tiglin compounds in the pH range (e.g. in sulfuric acid) and with increased rearrange into the Ε-forms using organic sulfinic acids as a temperature catalyst (cf. before, but this method already requires valuable Buckles, Mock and Locatell, Chem. Reviews 55 (1955) Fragrances as starting materials (tiglic acid or pp. 659-677). Tiglate), moreover, large apparatus and energy table effort. Because of the ice or Z configuration, great energy and equipment expenditure, insbetion Z-2-methyl-2-butenoic acid and its esters are special Z-thermal without lengthy fractional distillation more unstable than the corresponding trans- or 2-methyl-2-butenoic acid with a purity of over Ε-configuration (tiglic acid, tiglate). Produce the isomerization 95%, preferably over 98%. Before the fracture equilibrium is therefore a maximum of 10% Cation by crystallization, this is more common Configuration in the mixture. Because the angelica acid and way of the first and last distillate are separated Esters a few degrees below that of the Z- and E-2-methyl-2-butenoic acids Tiglic acid or the tiglate melt and in the case of the Ε-acid inevitably from the 2-methyl-3-busieden, the isomers can be created by means of an expensive tenenitrile. The ratio of the Z to the Rectification can be separated. This procedure gets 60 Ε acid at 75:25 to 81:19. there referred to as »isomerization distillation«. Is the implementation of the technical 2-methyl-2-bu- It was therefore the task of a simpler and tenenitrile with more concentrated sulfuric acid, d. H. so less Elaborate way of finding out from inexpensive - rather with a strength above 85%, carried out so occurs Geren starting substances in the greatest possible amount of rearrangement of the Z-2-methyl-2-butenoic acid to the E-acid ten to produce the Z-2-methyl-2-butenoic acid, where 65 a. The same applies if the temperature restrictions only the lowest possible contents of E-2-methyl-2-butene are not complied with. On the other hand, if you run the acid should be contained in the crude product. Reaction of the nitrile at temperatures below e.g. This task could now be carried out by the 70 ° C according to the invention or with strongly dilute acid, so